I have my Aunt's laptop that she needs me to look at. the laptop is around 5 years old and has been running well. only issue is the battery does not hold charge anymore. because of age of laptop I couldn't get her an exact replacement. I got her a battery from ebay that only lasted a week. I was wondering, can we power the laptop without the battery?
The battery doesn't have to hold a charge for the laptop to work. It just has to be in the laptop while mains is plugged in.
If you don't need it portable, you are already good to go.
Like Phillip said, buy from someone reputable.